Electrical switch construction and control system utilizing the same

ABSTRACT

An electrical switch construction having a pair of electrical contacts carried by a support and being adapted to be disposed in spaced relation relative to each other. A condition responsive device is carried by the support and has a movable member that moves relative to the support in response to changes in conditions being sensed by the device. The member has at least one part thereof formed of electrical conductive material and has at least another part thereof formed of electrically nonconductive material. Such member is disposed between the contacts whereby the one part thereof is adapted to be in contact with the contacts to provide an electrical circuit therebetween when the device senses a certain condition and the other part is adapted to be in contact with at least one of the contact means to prevent an electrical circuit between the contacts when the device senses another condition.

United States Patent 1 Sliger Nov. 6, 1973 337/393, 394, 315, 398, 399;ZOO/DIG. 25; 335/170 [56] References Cited UNITED STATES PATENTS1,559,022 10/1925 Wensley 337/315 1,890,909 12/1932 Lincoln 337/393Primary Examiner-Harold Broome Att0rney-Auzville Jackson, Jr. et al.

[57] ABSTRACT An electrical switch construction having a pair ofelectrical contacts carried by a support and being adapted to bedisposed in spaced relation relative to each other. A conditionresponsive device is carried by the support and has a movable memberthat moves relative to the support in response to changes in conditionsbeing sensed by the device. The member has at least one part thereofformed of electrical conductive material and has at least another partthereof formed of electrically non-conductive material. Such member isdisposed between the contacts whereby the one part thereof is adapted tobe in contact with the contacts to provide an electrical circuittherebetween when the device senses a certain condition and the otherpart is adapted to be in contact with at least one of the contact meansto prevent an electrical circuit between the contacts when the devicesenses another condition.

20 Claims, 8 Drawing Figures ELECTRICAL SWITCH CONSTRUCTION AND CONTROLSYSTEM UTILIZING THE SAME This invention relates to an improvedelectrical switch construction as well as to an electrical controlsystem utilizing such electrical switch construction or the like.

It is well known that separate electrical switches have been actuated bytemperature responsive devices of the power element type with theoperation of the switch being either the primary function of the deviceor the auxiliary function to the principal power producing function ofthe device. For example, such uses have been the actuation of warninglights, alarm devices or the like to indicate changes in temperature ofthe temperature responsive device or the actuation of secondary devicessuch as heaters, fans, etc. depending on the temperature of thetemperature responsive device.

Another use is to interrupt the electrical current through a resistancetype heater encircling the temperature responsive device to preventdamage to the device from excessive heating by the heater. Normally insystems of this type, a separate remote thermostatically operated deviceis incorporated to respond to the tem perature of a medium to becontrolled, such as the temperature of the air space. The temperatureresponsive device of the electrical switch is used, in turn, to providethe mechanical driving force to position a valve or the like permittinga flow of a heating or cooling medium through a heat exchanger to effectthe air space being controlled. Without the interruption of the heatercurrent by the separate switch during periods of prolonged thermostaticdemand for full power element movement, the resistance heater wouldcontinue to heat the power producing temperature responsive devicewithout restraint. With the switch employed, however, the current to theheater can be discontinued at the maximum allowable power producingtemperature responsive device stroke. With the current interrupted bythe switch, the temperature responsive device will cool until the switchcontacts reach a closed position and current is again communicated tothe heater and the cycle is repeated.

It is a feature of this invention to provide an improved electricalswitch construction to be utilized in the above manner as well as forother systems and purposes as desired.

In particular, it is a feature of this invention to provide anelectrical switch construction wherein the movable element of atemperature responsive device has portions thereof that are conductiveand nonconductive for respectively making and breaking-the electricalcircuit between a pair of contacts disposed in engagement with themovable member.

For example, one embodiment of the electrical switch construction ofthis invention comprises a support means carrying a pair of electricalcontact means adapted to. be disposed in spaced relation relative toeach other. A condition responsivedevice is carried by tact with thecontact means to provide a circuit therebetween when the device senses acertain condition and the other part is adapted to be in contact with atleast one of the contact means to prevent a circuit between the contactmeans when the device senses another condition.

Accordingly, it is an object of this invention to provide an electricalswitch construction having one or more of the novel features'set forthabove or hereinafter shown or described.

Another object of this invention is to provide an electrical systemutilizing such an electrical switch construction.

Other objects, uses and advantages of this invention are apparent fromreading of this description which proceeds with reference to theaccompanying drawing forming a part thereof and wherein FIG. 1 is a sideview, partially in cross-section, illustrating one embodiment of theelectrical switch construction of this invention as utilized in anelectrical control system of this invention which is illustratedschematically in FIG. 1.

FIG. 2 is a view similar to FIG. 1 and illustrates the electrical switchconstruction in another operating condition thereof.

FIG. 3 is a top view of the electrical switch construction of FIG. 1.

FIG. 4 is a view similar to FIG. 1 and illustrates another embodiment ofthe electrical switch construction of the invention.

FIG. 5 is a view similar to FIG. 1 and illustrates another embodiment ofthe electrical switch construction of this invention.

FIG. 6 is a top view of electrical switch control of FIG. 5.

FIG. 7 is a view similar to FIG. 1 and illustrates another embodiment ofthe electrical switch construction of this invention.

FIG. 8 is a view similar to FIG. 1, except that the same is in fullcross-section, and illustrates another electricalswitch construction ofthis invention.

While the various features of this invention are hereinafter describedand illustrated as being particularly adapted for controlling aparticular electrical control system, it is to be understood that thevarious features of this invention can be utilized singly or in anycombination thereof to provide means for controlling other electricalcontrol systems as desired.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings, because the drawings are merely utilized toillustrate one of the the support means and has a movable member thatmoves relative to the support means in response to changes in conditionsbeing sensed by the device. The member has at least one part thereofformed of electrically conductive material and has at least another partthereof formed of electrically non-conductive material. The member isdisposed between the contact means whereby the one part thereof isadapted to be in conwide variety of uses of this invention.

Referring now to FIG. 1, one embodiment of the electrical switchconstruction of this invention is generally indicated by the referencenumeral 10 and is illustrated as being utilized in an electrical controlsystem of this invention that is generally indicated by the referencenumeral 11 and comprises an electrical power source 12, a resistanceheater l3 and a temperature responsive device 14. v

The electrical switch construction 10 0s this invention comprises a pairof contact means 15 and 16 respectively having terminal ends 17 and 18interconnected to electrical leads 19 and 20.

The lead 20 is interconnected to one side 21 of the electrical powersource 12 while the other side 22 of the electrical power source 12 isinterconnected by a lead 23 to one side 24 of the electrical resistanceheater 13. The other side 25 of the heater coil 13 is interconnected bya lead 26 to one side 27 of the temperature responsive device 14. Theother side 28 of the temperature responsive device 14 is interconnectedto the lead 19.

Thus, it can be seen that when a circuit is completed between thecontact means 15 and 16 of the electrical switch construction of thisinvention in a manner hereinafter set forth and the temperatureresponsive device 14 senses that the temperature of the air surroundingthe same is below the set temperature thereof and is thusinterconnecting the lead 26 to the lead 19, electrical current from thepower source 12 is adapted to flow through the resistance heater 13 andheat the electrical switch construction 10 of this invention to causethe same to extend a plunger or movable member 29 thereof in a mannerhereinafter set forth and as illustrated in FIG. 2 to cause a suitablevalve or other structure (not shown) of a heat exchanger means (notshown) to supply heated air or the like to tend to raise the temperatureof the space being heated thereby. When the temperature responsivedevice 14 is satisfied, the same disconnects the lead 26 from the lead19 so that no further current flows through the heater means 13 untilthe thermostat 14 again demands an increase in temperature.

When the circuit through the coil 13 is discontinued, the movable member29 normally assumes the retracted position illustrated in FIG. 1 wherethe same is in its non-extended position and is not operating the heatexchanger valve.

The electrical switch construction 10 of this invention includes atemperature responsive device or power element 30 that operates on thewell known principal of the piston and cylinder temperature responsivedevice wherein the piston thereof is extended from the cylinder uponan-increase in sensed temperature be- 7 cause of a thermally responsivewax charge material in the cylinder expanding upon the increase intemperature thereof and with the piston retracting into the cylinderupon a decrease in sensed temperature because the thermally responsivewax charge material in the cylinder contracts upon a decrease intemperature thereof.

Thus, it can be seen that the temperature responsive device 30 includesan outer cylinder housing 31 formed of a plurality of different sizedcylindrical sections 32, 33, 34 and 35 with the piston rod, stem ormovable member 29 projecting out of a suitable opening formed in theupper end 36 of the upper cylindrical section 32 of the housing 31.

The movable member 29 has a lower end 37, FIG. 8, received within a stemseat 38 formed of rubber or other resilient material disposed within thehousing 31 and having its lower end 39 engaging against a flexiblediaphragm 40 separating the seat member 38 from a fusible, thermallyexpansive material 41 disposed in the lower end of the housing 31. Forexample, such fusible,

thermally expansive material 41 can comprise a wax containing powderedmetal, heat conducting material which expands as the temperature thereofis increased. Such increase in temperature of the thermally expansivewax charge material 41 causes the same to expand and force the pistonmember 29 to move upwardly in the manner illustrated in FIG. 2 whereaswhen the thermally responsive wax charge material 41 senses a decreasein temperature, the same contracts and permits the piston member 29 toassume the retracted position illustrated in FIG. 1.

The electrical switch construction 10 includes an annular support member42 formed of electrically nonconductive material and being press fittedover the upper cylindrical part 32 of the housing 31 in the mannerillustrated in FIG. 1 or is otherwise secured thereto in any desiredmanner. The contact means 15 and 16 can each comprise a one pieceelectrically conductive member respectively having the terminal portions17 and 18 thereof passing through suitable openings in the supportmember 42 so as to be secured thereto and being suitably bent so thatelbow portions 43 and 44 thereof are respectively adapted to be disposedin sliding engagement with the movable member 29 of the temperatureresponsive element 30. The contact means 15 and 16 are so formed thatthe same have a natural bias to continuously urge the elbow portions 43and 44 thereof respectively into contact with the movable member 29.

In the embodiment of the electrical switch construction 10 illustratedin the drawings, the elbow portions 43 and 44 of the contact means 15and 16 are respectively disposed in different parallel planes passingtransversely to the direction of movement of the member 29.

The piston member 29 of the thermally responsive element 30 is made ofalternately spaced nonelectrically conductive material, such as nylon orother plastic material, and electrically conductive material such ascopper, copp'er alloys or the like. For example, the piston member 29has one conductive part 45 spacing a pair of non-conductive parts 46 and47 from each other while being disposed in stacked aligned relation.

The conductive part 45 of the piston element 29 is of such a length inrelation to the elbows 43 and 44 of the contact means 15 and 16 thatwhen the temperature responsive device 30 is in a cool or retractedcondition thereof wherein the piston member 29 is in its fully retractedposition relative to the cylinder means 31, the conductive part 45 isengaged by both elbows 43 and 44 of the contact means 15 and 16 so thatan electrical circuit is provided or completed between the contact means15 and 16. However, upon the heating of the temperature responsivedevice 30, the piston 29 is extended in the manner illustrated in FIG. 2so that the non-conductive portion 47 now makes contact with at leastthe elbow 43 of the contact means 15 and thereby prevents the making ofthe electrical circuit between the contact means 15 and 16.

The operation of the electrical switch construction 10 as utilized inthe control system 11 of FIGS. 1 and 2 will now be described.

As illustrated in FIG. 1, when the temperature responsive device 14 issatisfied, the same prevents electrical connection between leads 26 and19 so that no current flows through the resistance heater 13 and thepower element 30 is in its non-heated condition whereby the pistonmember 29 thereof is in the fully retracted position illustrated inFIG. 1. Thus, the conductive part 45 of the member 29 is in contact withthe contact means 15 and 16 so that an electrical circuit is completedtherebetween. When the thermostat 14 senses a decrease in temperaturebelow-the set temperature' thereof, the same interconnects the leads 26and 19 together so that the power source 12 is now adapted to sendcurrent through the heater coil 13 which heats the temperatureresponsive device 30 and causes the piston 29 thereof to extend in themanner illustrated in FIG. 2. Such extended piston 29 operates suitablevalve means or the like (not shown) when in its extended condition tosupply heat to the space being sensed by the temperature responsivedevice 14. However, since the piston 29 of the temperature responsivedevice 30 is now in its extended condition, it can be seen that thenon-conductive part 47 thereof is now engaged by the elbow 43 of thecontact means 15 so that the electrical circuit between the contactmeans 15 and 16 is broken. Thus, no current can flow through the heatermeans 13 even though the thermostat 14 may not be satisfied by theincrease in heated air being directed thereto whereby the leads 26 and19 are still being electrically connected together by the thermostat 14.The opening if the thermostat 14 is still interconnecting the leads l9and 26 together, current can again flow through the heater coil 13 toheat up the power element,30 and, thus, again extend the piston 29 inthe previously described manner whereby the temperature responsivedevice is adapted to be cycled back and forth between its extended andnon-extended condition of the piston member 29. Such cycling of thetemperature responsive device 30 prevents damage thereto from excessiveheating by the heater l3 sothat the device 30. will not be subjected tolong periods where the piston 29 thereof is fully extended in its powerstroke should the temperature responsive device 14 have prolongedtemperature requiring periods.

Therefore, it can be seen that the improved electrical switchconstruction 10 of this invention can be formed of a relatively fewparts to operate in a unique manner for opening and closing a circuitbetween a pair of-electrical contact means.

While the electrical switch constructionlo-has been previously describedas opening the circuit between'the contact means upon the extending ofthe movable member of the temperature responsive device, it is to beunderstood that the movable member could be so constructed and arrangedas the same will complete the circuit between the contact means onlywhen extended and prevents a circuit therebetween when retracted;

For example, another electrical switch construction of this invention isgenerally indicated-by the reference numeral 10A in FIG. 4 and partsthereof similar to the switch construction 10 previously described areindicated by like reference numerals followed by the reference letter A.

As illustrated in FIG. 4, the conductive part 45A and non-conductiveparts 47A and 46A of the movable member 29A of the temperatureresponsive device 30A are so constructed and arranged that when themovable member 29A is in the fully retracted position illustrated inFIG. 4, the elbow 43A of the contact means A is in contact with theconductive part 45A but the elbow 44A of the contact means 16A isinengagement with the non-conductive part 46A so that a circuit cannot becompleted between the contact means 15A and 16A when the movable member29A is in its retracted condition. However, upon heating of the element30A in the manner previously described, the piston 29A is extended insuch a manner that the conductive part 45A can now be engaged by bothelbow portions 43A and 44A of the contact means 15A and 16A so that anelectrical circuit is completed therebetween.

While the electrical switch constructions 10 and 10A of this inventionhave been previously described as having only two contact means, it isto be understood that the electrical switch constructions of thisinvention can have additional contact means carried by the support meansand engaging against the movable member of the temperature responsivedevice.

For example, reference is now made to FIGS. 5 and 6 wherein anotherelectrical switch construction of this invention is generally indicatedby the reference numeral 10B and parts thereof similar to the switchconstructions 10 and 10A previously described are indicated by likereference numerals followedby the reference letter B.

As illustrated in FIG. 5, a third contact means 48 is carried by thesupport means 428 and has its elbow 49 disposed in engagement with themovable part 298 of the temperature responsive device 308.

The conductive part 45B and non-conductive parts 468 and 47B of thepiston member 298 are so constructed and arranged that when thethermostatic device 30Bis-not being heated and the piston member 29B isin its fully retracted condition as illustrated in FIG. 5, theconductive part 458 is being engaged by the elbow portions 438 and 44Bof the contact means 158 and 168 so as to provide an electrical circuittherebetween while the elbow 49 of the third contact means 48 is inengagement with the non-conductive-part 468 so that no electricalcircuit is completed between the contact means 48 and either one of thecontact means 158 and 16B.

Upon heating of the temperature responsive device 30B to a certaintemperature, the piston member 298 will be extended part way between itsfully retracted and fully extended conditions so that the nonconductivepart 478 is now engaged by the elbow 43B of the contact means 158whereby an electrical circuit is prevented between the contact means 158and 168 by the non-conductive part 478 and the elbow 49 of the thirdcontact meand 48 remains in contact with the non-conductive portion 468so that the contact means 48 is not electrically connected to either ofthe contact means 158 and 168.

However, upon further heating of the temperature responsive device 308so that the piston member 493 is in its fully extended condition, theconductive part 458 of the member 298 is now so positioned that theelbows 44B and 49 of thecontact means 168 and 48 are now engaging theconductive part 458 whereby an cylinder temperature responsive device ofthe power element type, the electrical switch construction of thisinvention can be moved by other condition responsive devices if desired.

For example, reference is made to FIG. 7 wherein another electricalswitch construction of this invention is generally indicated by thereference numeral C and parts thereof similar to the switchconstructions 10, 10A and 10B previously described are indicated by likereference numeral as followed by the reference letter ILCiQ Asillustrated in FIG. 7, the movable member 29C has its lower end 50secured to a movable wall 51 of a vapor filled bellows 52 carried withina housing means 53 having its neck portion 54 telescopically receivingthe annular support means 42C previously described and that carries thecontact means C and 16C.

The movable member 29C has the conductive parts 45C and non-conductiveparts 46C and 47C previously described but can also have an additionalconductive part 55 and a non-conductive part 56 as illustrated so thatthe non-conductive parts will prevent an electrical circuit between thecontact means 15C and 16C in the manner previously described indifferent positions of the movable member 29C as caused by the collapseor expansion of the bellows construction 52. Likewise, the conductiveparts 45C and 55 can provide an electrical circuit between the contactmeans 15C and 16C when the same are so positioned by the bellows 52 tobe disposed in contact with the contact means 15C and 16C in the mannerpreviously described.

While the contact means of the electrical constructions of thisinvention have been previously described as each being a one-piecemember having an elbow contacting the movable member of the temperatureresponsive device, it is to be understood that other forms of contactmeans can be utilized if desired.

For example, reference is now made to FIG. 8 wherein another electricalswitch construction of this invention is generally indicated by thereference numeral 10D and parts thereof similar to the electrical switchconstructions 10, 10A, 10B and 10C previously described are indicated bylike reference numerals followed by the reference letter D.

As illustrated in FIG. 8, the contact means 15D and 16D each comprises aone-piece bent member providing the terminal portions 17D and 18Dpreviously described but with the same carrying conductive contactmembers 57 and 58 at the upper end thereof for engagement with themovable member 29D. For example, such contacts 57 and 58 can each beformed of a highly electrically conductive material, such as silver,gold, copper, copper alloys, etc., and is attached to the leaf contactmember 15D and 16D so that the same will bear against the movable member29D.

In all of the switch constructions previously described, it may be foundthat the. non-conductive portionsof the movable pistonmember of thetemperature responsive device can be formulated with an abrasive typematerial such as fiberglass, etc. which will effectively clean thecontacting portions of the contact means each time during the movementof the nonconductive portions past the engaging part of the contactmeans.

Thus, it can be seen that this invention not only provides an improvedelectrical switch construction that is adapted to readily make and breakan electrical circuit between a pair of contact means thereof inresponse to a condition being sensed by a condition responsive device ofthe construction, but also this invention provides an electrical controlsystem utilizing such an electrical switch construction. v

While the form of the invention now preferred has been described asrequired by the patent statute, it is to be understood that other formscan be utilized and all come within the scope of the appended claims.

What is claimed is:

1. An electrical switch construction comprising support means, a pair ofelectrical contact means carried by said support means and being adaptedto be disposed in spaced relation relative to each other, and acondition responsive device carried by said support means and having amovable member that moves relative to said support means in response tochanges in conditions being sensed by said device, said member havingone part thereof formed of electrically conductive material and havinganother part thereof formed of electrically non-conductive material,said member being disposed between said contact means whereby said onepart thereof is adapted to be in contact with said pair of contact meansto provide a circuit therebetween when said device senses a certaincondition and said other part is adapted to be in contact with only oneof said pair of contact means to prevent a circuit between said pair ofcontact means when said device senses another condition, said contactmeans respectively engaging said member in different parallel planesthat pass transversely to the direction of movement of v said partswhereby the other of said contact means is always in contact with saidone part of said member when said device is sensing either of said twoconditions.

2. An electrical switch construction as set forth in claim 1 whereinsaid member has said parts thereof disposed adjacent each other inaligned relation.

3. An electrical switch construction as set forth in claim 2 whereinsaid conductive part is disposed intermediate a pair of non-conductiveparts of said member of which one comprises said other part of saidmember.

4. An electrical switch construction as set forth in claim 3 wherein athird contact means is carried by said support means and engages saidmember in a plane different from but parallel to said first-namedplanes.

5. An electrical switch construction as set forth in claim 1 whereinsaid condition responsive device is a temperature responsive device.

6. An electrical switch construction as set forth in claim 6 whereinsaid parts of said member are so constructed and arranged that saidnon-conductive part of said member is moved into said contact with saidone contact means when said device senses a temperature above a certaintemperature.

7. An electrical switch construction as set forth in claim 5 whereinsaid parts of said member are so constructed and arranged that saidnon-conductive part of said member is moved into said contact with saidone contact means when said device senses a temperature below a certaintemperature.

8. An electrical switch construction as set forth in claim 1 whereinsaid device comprises a piston and cylinder temperature responsivedevice wherein said piston is extended from said cylinder upon anincrease in sensed temperature and is retracted into said cylinder upona decrease in sensed temperature, said piston comprising said movablemember.

9. An electrical switch construction as set forth in claim 8 whereinsaid support means comprises an annular member telescoped and secured onsaid cylinder of said temperature responsive device.

10. An electrical switch construction as set forth in claim 4 whereinsaid third contact means engages said one part of said member when saiddevice is sensing said other condition whereby said one part is adaptedto provide a circuit between said other contact means and said thirdcontact means when said device is sensing said other condition, saidthird contact means engaging the other of said pair of non-conductiveparts of said member when said device is sensing said certain conditionswhereby said other non-conductive part is adapted to prevent a circuitbetween said other contact means and said third contact means when saiddevice is sensing said certain conditions.

11. An electrical control system comprising an electrical power source,an electrical circuit interconnected to said source, and an electricalswitch construction disposed in said electrical circuit and havingsupport means, a pair of electrical contact means carried by saidsupport means and being adapted to be disposed in spaced relationrelative to each other, and a condition responsive device carried bysaid support means and having a movable member that moves relative tosaid support means in response to changes in conditions being sensed bysaid device, said member having one part thereof formed of electricallyconductive material and having another part thereof formed ofelectrically nonconductive material, said member being disposed betweensaid contact means whereby said one part thereof is adapted to be incontact with said pair of contact means to provide a circuittherebetween and thereby complete said electrical circuit when saiddevice senses a certain condition and said other part is adapted to bein contact with only one of said pair of contact means to prevent acircuit between said pair of contact means and thereby open saidelectrical circuit when said device senses another condition, saidcontact means respectively engaging said member in different parallelplanes that pass transversely to the direction of movement of said partswhereby the other of said contact means is always in contact with saidone part of said member when said device is sensing either of said twoconditions.

12. An electrical control system as set forth in claim 1 1 wherein saidmember has said parts thereof disposed adjacent each other in alignedrelation.

13. An electrical control system as set forth in claim 12 wherein saidconductive part is disposed intermediate a pair of non-conductive partsof said member of which one comprises said other part of said member.

14. An electrical control system as set forth in claim 13 wherein athird contact means is carried by said support means and engages saidmember in a plane different from but parallel to said first-namedplanes.

15. An electrical control system as set forth in claim 11 wherein saidcondition responsive device is a temperature responsive device.

16. An electrical control system as set forth in claim 15 wherein saidparts of said member are so constructed and arranged that saidnon-conductive part of said member is moved into said contact with saidone contact means when said device senses a temperature above a certaintemperature.

17. An electrical control system as set forth in claim 15 wherein saidparts of said member are so constructed and arranged that saidnon-conductive part of said member is moved into said contact with saidone contact means when said device senses a temperature below a certaintemperature.

18. An electrical control system as set forth in claim 1 1 wherein saiddevice comprises a piston and cylinder temperature responsive devicewherein said piston is extended from said cylinder upon an increase insensed temperature and is retracted into said cylinder upon a decreasein sensed temperature, said piston comprising said movable member.

19. An electrical control system as set forth in claim 18 wherein saidsupport means comprises an annular member telescoped and secured on saidcylinder of said temperature responsive device.

20. An electrical control system as set forth in claim 14 wherein saidthird contact means engages said one part of said member when saiddevice is sensing said other condition whereby said one part is adaptedto provide a circuit between said other contact means and said thirdcontact means when said device is sensing said other condition, saidthird contact means engaging the other of said pair of non-conductiveparts of said member when said device is sensing said certain conditionswhereby said other nonconductive part is adapted to prevent a circuitbetween said other contact means and said third contact means when saiddevice is sensing said certain conditions.

1. An electrical switch construction comprising support means, a pair ofelectrical contact means carried by said support means and being adaptedto be disposed in spaced relation relative to each other, and acondition responsive device carried by said support means and having amovable member that moves relative to said support means in response tochanges in conditions being sensed by said device, said member havingone part thereof formed of electrically conductive material and havinganother part thereof formed of electrically non-conductive material,said member being disposed between said contact means whereby said onepart thereof is adapted to be in contact with said pair of contact meansto provide a circuit therebetween when said device senses a certaincondition and said other part is adapted to be in contact with only oneof said pair of contact means to prevent a circuit between said pair ofcontact means when said device senses another condition, said contactmeans respectively engaging said member in different parallel planesthat pass transversely to the direction of movement of said partswhereby the other of said contact means is always in contact with saidone part of said member when said device is sensing either of said twoconditions.
 2. An electrical switch construction as set forth in claim 1wherein said member has said parts thereof disposed adjacent each otherin aligned relation.
 3. An electrical switch construction as set forthin claim 2 wherein said conductive part is disposed intermediate a pairof non-conductive parts of said member of which one comprises said otherpart of said member.
 4. An electrical switch construction as set forthin claim 3 wherein a third contact means is carried by said supportmeans and engages said member in a plane different from but parallel tosaid first-named planes.
 5. An electrical switch construction as setforth in claim 1 wherein said condition responsive device is atemperature responsive device.
 6. An electrical switch construction asset forth in claim 6 wherein said parts of said member are soconstructed and arranged that said non-conductive part of said member ismoved into said contact with said one contact means when said devicesenses a temperature above a certain temperature.
 7. An electricalswitch construction as set forth in claim 5 wherein said parts of saidmember are so constructed and arranged that said non-condUctive part ofsaid member is moved into said contact with said one contact means whensaid device senses a temperature below a certain temperature.
 8. Anelectrical switch construction as set forth in claim 1 wherein saiddevice comprises a piston and cylinder temperature responsive devicewherein said piston is extended from said cylinder upon an increase insensed temperature and is retracted into said cylinder upon a decreasein sensed temperature, said piston comprising said movable member.
 9. Anelectrical switch construction as set forth in claim 8 wherein saidsupport means comprises an annular member telescoped and secured on saidcylinder of said temperature responsive device.
 10. An electrical switchconstruction as set forth in claim 4 wherein said third contact meansengages said one part of said member when said device is sensing saidother condition whereby said one part is adapted to provide a circuitbetween said other contact means and said third contact means when saiddevice is sensing said other condition, said third contact meansengaging the other of said pair of non-conductive parts of said memberwhen said device is sensing said certain conditions whereby said othernon-conductive part is adapted to prevent a circuit between said othercontact means and said third contact means when said device is sensingsaid certain conditions.
 11. An electrical control system comprising anelectrical power source, an electrical circuit interconnected to saidsource, and an electrical switch construction disposed in saidelectrical circuit and having support means, a pair of electricalcontact means carried by said support means and being adapted to bedisposed in spaced relation relative to each other, and a conditionresponsive device carried by said support means and having a movablemember that moves relative to said support means in response to changesin conditions being sensed by said device, said member having one partthereof formed of electrically conductive material and having anotherpart thereof formed of electrically nonconductive material, said memberbeing disposed between said contact means whereby said one part thereofis adapted to be in contact with said pair of contact means to provide acircuit therebetween and thereby complete said electrical circuit whensaid device senses a certain condition and said other part is adapted tobe in contact with only one of said pair of contact means to prevent acircuit between said pair of contact means and thereby open saidelectrical circuit when said device senses another condition, saidcontact means respectively engaging said member in different parallelplanes that pass transversely to the direction of movement of said partswhereby the other of said contact means is always in contact with saidone part of said member when said device is sensing either of said twoconditions.
 12. An electrical control system as set forth in claim 11wherein said member has said parts thereof disposed adjacent each otherin aligned relation.
 13. An electrical control system as set forth inclaim 12 wherein said conductive part is disposed intermediate a pair ofnon-conductive parts of said member of which one comprises said otherpart of said member.
 14. An electrical control system as set forth inclaim 13 wherein a third contact means is carried by said support meansand engages said member in a plane different from but parallel to saidfirst-named planes.
 15. An electrical control system as set forth inclaim 11 wherein said condition responsive device is a temperatureresponsive device.
 16. An electrical control system as set forth inclaim 15 wherein said parts of said member are so constructed andarranged that said non-conductive part of said member is moved into saidcontact with said one contact means when said device senses atemperature above a certain temperature.
 17. An electrical controlsystem as set forth in claim 15 wherein said parts of said member are soconstructed and Arranged that said non-conductive part of said member ismoved into said contact with said one contact means when said devicesenses a temperature below a certain temperature.
 18. An electricalcontrol system as set forth in claim 11 wherein said device comprises apiston and cylinder temperature responsive device wherein said piston isextended from said cylinder upon an increase in sensed temperature andis retracted into said cylinder upon a decrease in sensed temperature,said piston comprising said movable member.
 19. An electrical controlsystem as set forth in claim 18 wherein said support means comprises anannular member telescoped and secured on said cylinder of saidtemperature responsive device.
 20. An electrical control system as setforth in claim 14 wherein said third contact means engages said one partof said member when said device is sensing said other condition wherebysaid one part is adapted to provide a circuit between said other contactmeans and said third contact means when said device is sensing saidother condition, said third contact means engaging the other of saidpair of non-conductive parts of said member when said device is sensingsaid certain conditions whereby said other nonconductive part is adaptedto prevent a circuit between said other contact means and said thirdcontact means when said device is sensing said certain conditions.